A series of experiments is proposed to investigate sensory and perceptual processes in speech communication. These experiments will attempt to clarify the mechanisms of perceptual organization of the speech signal, which operate early in the processing of acoustic stimuli. Such processes organize phonetic signals by defining coherent patterns of stimulus elements, establishing an auditory representation appropriate for phonetic recognition. Two sources of hypotheses about organizational mechanisms active in the perception of speech will be investigated. Psychoacoustic research on auditory organization will motivate a number of empirical analyses of the role of stream formation in the perception of speech signals. Perceptual and acoustical studies of vocally produced sounds will also be used to consider organizational mechanisms that may be tailored specifically to speech signals. The four projects that are planned will investigate the contingency of phonetic perception on the range of signal frequency variation; the relative disposition to organize sinewave replicas of speech auditorily or phonetically; the growth of attention to time-verying spectrum properties; and the perception of spontaneously produced speech. These studies will identify the means by which the perceptual integrity of the speech signal is established and maintained, thereby contributing to our understanding of speech perception by normal human adults.